Prime Minister Narendra Modi wants to see a clean India. To fulfill this ambition, he has launched the Swachh Bharat (Clean India) mission, a supply-side initiative which, among other things, plans to build 110 million toilets across India between 2014 and 2019. The underlying presumption is India has a large number of poor people who cannot afford to construct a toilet, and there is thus a need for government intervention.

A year down the line, little has changed. In spite of the government constructing 8 million toilets in 2015, worldwide, India still has the highest number of people defecating in the open, around 600 million. In a first ever scientific attempt we can determine why this is the case (for a detailed analysis, see our paper here).

Why Hindus are less likely to use toilets

The other important finding is that religion, caste and culture have an important role in determining whether any particular individual is likely to use toilets. Our research demonstrates that Muslim households are 5.4 times more likely to use a toilet than Hindu ones. Even Christian households are 1.3 times more likely to adopt a toilet in comparison to their Hindu counterparts. Hindu households have the lowest coverage of sanitation facilities in comparison to other religions.

Open defecation among Hindu households is linked to the caste system...

This result is surprising, as Indian Muslims are on average both poorer and less educated than Indian Hindus. There are two plausible reasons for it. First, there may be a historical path-dependency related to religion that encourages open defecation among Hindus. Open defecation among Hindu households is linked to the caste system, where the customary circumvention of excreta is sustained by keeping defecation away from the house and entrusting the cleanup job to the so-called "untouchables" or "lower" castes. Many rural Hindu households are averse to the idea of having toilets in the same building as their living quarters.

The importance of culture and behavioural attitudes is evident from the Bangladesh experience. Although it has a much lower per-capita income, Bangladesh has a significantly superior sanitation rate to that of India. Only 3% of the population in Bangladesh defecates in the open in comparison to India's 50%. The majority of Bangladeshis are Muslim. Culturally, Muslims are accustomed to offering prayer (azan) more than four times a day. And each time they do, they have a practice of washing their hands and feet, and physically cleaning themselves. A campaign that ran in Bangladesh, pointing out that defecating in the open may end up contaminating crops, also helped as it left many disgusted at the thought. Muslim women are more likely to use toilets than their male counterparts due to the perceived benefits of dignity and safety.

There is a second approach to understanding why Indian Muslims are more likely to use toilets. We find Muslims are more likely to live in urban areas than Hindus are. The conditional probability of a household residing in a urban area is 0.45 for Hindu and 0.55 for Muslims. Spatially, households living in urban areas are 19 times more likely to use a toilet in comparison to their rural counterparts.

The caste factor

The caste system matters. Scheduled Caste (SC), Scheduled Tribe (ST) and Other Backward Class (OBC) households have a lower probability of using a toilet when compared with households from general caste Hindu, Muslims and Christians. People from SC, ST and OBC communities are more likely to come from a rural or tribal background. These communities live in relatively inaccessible areas of the nation, and thus have lower access to public goods such as water connectivity, in comparison to others.

Certain communities in Kerala and Meghalaya practice matriarchy, where women have power...This may explain the greater prevalence of toilet users...

Our results suggest that for households living in rural areas and the countryside, the conditional probability that these households belong to SC, ST or OBC is more than 0.60, in comparison to 0.41 for people from other communities. The level of abject poverty is higher among these castes, which could be another potential reason for poorer sanitation coverage among SC, ST and OBCs.

Culture and location

The likelihood of households in the Northeast Indian states of Manipur, Mizoram, Tripura and Meghalaya, and the southern state of Kerala using a toilet facility is much higher than that of a household in Delhi. In fact, in Kerala communities like the Nairs and Ezhavas, and in Meghalaya the Khasi, Jaintias, and the Garo tribes (comprising a majority of the population) practice matriarchy, where women have power in activities relating to allocation, exchange and production. This can also explain the greater prevalence of toilet users in these states. In contrast, households from Rajasthan, Jammu & Kashmir, Himachal Pradesh, Jharkhand, Chhattisgarh and Tamil Nadu are less likely to use toilets in comparison to a household from Delhi.

In fact, an important observation is people living in rural areas are accustomed to the habit of defecating in the open. In rural Maharashtra and Madhya Pradesh, tribal people use toilets as a storeroom, as that is the only concrete structure available. Bizarre as it may sound, in one instance, the toilet was used as a place of worship as the lady felt the concrete structure was most elegant room in her ramshackle home.

All these ground realities make a strong case for imparting education and public awareness, so that behavioural attitudes can be changed.

Policy implications

These results have some obvious policy implications. First, the government should concentrate on creating a demand for the use of toilets. Policymakers must ensure that a larger proportion of funds are directed towards social marketing and educating people about hygiene. Intervention should target areas/districts with more per-capita open defecation rather than merely building toilets.

Policymakers must ensure that a larger proportion of funds are directed towards social marketing and educating people about hygiene.

Second, as female literacy is important, it would be wise to target women and actively involve them in policymaking. Our study show, a household in which a woman has attained higher education (18 years of schooling) is 3.1 times more likely to use a toilet.

Finally, there is a need for government policies specifically focusing on improving sanitation in rural areas. These policies can be combined with rural education initiatives, along with measures to improve availability of water among households in villages.